public delegate void SROptionsPropertyChanged(object sender, string propertyName);

public partial class SROptions
{
    private static readonly SROptions _current = new SROptions();

    public static SROptions Current
    {
        get { return _current; }
    }

    public event SROptionsPropertyChanged PropertyChanged;
#if UNITY_EDITOR
    [JetBrains.Annotations.NotifyPropertyChangedInvocator]
#endif
    public void OnPropertyChanged(string propertyName)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, propertyName);
        }
    }
}